Control device



E. J. DILLMAN GNTROL DEVICE Filed May 17, 19:54

May 11, 1937.

Patented May 11, 1937 UNITED STATES PATENT CFFICE Application May 17, 1934, Serial No. 726,036

1'8 Claims.

My invention relatesr to new and. useful imi provements in control devices such as. an electric switch having automatically operable means for actuating the same..

for determining the force exerted by the automatic means which will operate the switch to make and break contact.

Another object is toV provide means for determ mining the force exerted by the automatic means at which contact will. be broken without aiecting the force exerted by the automaticv means at which Contact will be made.

Another object is to provide means for de- L; termning the force exerted by the automatic means at which Contact will be made without affecting the force exerted by the automatic means at which contact will be broken.

Another object is to provide means for actuating the switch irrespective of the operation: of the switch by the automatic means.

Another object is to provide a snap acting safety means for actuating the switch.

Another object is to provide adjustable mag,-

netic means for regulating the operation of the M switch.

The invention consists in the improved construction and combination of parts, to be more fully described` hereinafter and the novelty of w which will be particularly pointed out and distinctly claimed.

In the accompanying drawing, to be taken as a part of this specification, I have fully and clearly illustratedy a preferred embodiment of my invention, i-n which drawing- Figure l is a view in longitudinal vertical central section ofthe control device of my invention;

Fig. 2 is a View in section on the line 22 of Fig. l;

Fig. 3' is a detail View in section taken on the line 3-3` of Fig. l, and

Fig. 4 is a detailv view in section taken on the line 4 4 of Fig. 1.

Referring to the drawing by characters of reference, I designates generally a supporting structure such as a rectangular housing of electric insulating materialv having opposite endv walls 2, 3 joined by top and bottom walls 4, 5 respectively and closed by a rear wall 5. The m housing is preferably closed at its. front by a cover member or plate T, also of electric insulating material. Through the bottom wall 5 of the housing adjacent the end wall 3, there is an opening 8 whichv is closed by a cup-shaped container 9 having a marginal rim or flange which engages f An object of my invention isv tov provide meansy the outer or under face of the wall 5 around opening 8 and by which the container is rigidly secured to the housing as by screws I0. The container 9 has a movable end wall II which forms the head of a metal bellows I2 positioned con- 5, centrically within the container 9. 'I'he upper end of the bellows I2. is sealed to an annular plate I3 which is secured and sealed at its outer periphery to the inside face of the side wall of container 9 adjacent its rim so as to provide m within the container an expansible chamber I4. The bottom wall of the container 9 is provided with a tting I5 having a bore IB therethrough n opening into the chamber I4 for the admission of uid under pressure to actuate the wall I I. The 15 head II is provided with a stop member II such as a post which extends into the bore I5 and is provided. with a head I8 which cooperates with an annular shoulder I9 in the bore I0 to limit collapse of bellows I2 and expansion of the chamber 20 I4.. A coil spring 20 surrounds the post II and is held under compression between the head II and the fittingA I5 and serves to oppose collapse ofy the chamber I4 and expansion of the bellows I2 upon reduction of pressure in the chamber I4. 25 Extending upwardly from the wall II within the bellows I2 there is a thrust member or operating rod 2| which projects through the opening 8 into housing I and terminates adjacent the top housing wall 4'. Surrounding the thrust member 2I there is a helical coil spring 22 which seats on an abutment member or cup plate 23 which rests on an annular upward facing shoulder 24 on the thrust member. The upper end of the spring 22 is housed within a cup member 25 and bears at its upper end against the end wall 26 of the cup member which is apertured for the free passage of the thrust member therethrough. Positioned between the thrust member 2I and the end housing wall 3 there is an adjustment lever 21 which w is pivotally supported on a shaft 28 secured in the` rear housing wall 6. The lever 21 is preferably' U-sha-ped, having its arms of which but one is shown, and which are joined by` a cross member 29, extending on opposite sides of the cup member 25 and bearing, as at 30, at diametrically opposite points on the top face of a circumferential ange 3l projecting from the lower end of the cup member 25. An adjustment screw 32 which is adjustably screw-threaded in 50 a metal insert 33 in the end wall 3 is operatively connected to the lever 2'I by a pin 34 which bears at its opposite ends in recesses in the screw 32 and the cross member 29. The upper end of the thrust member 2| terminates between the op- 5,-

posite depending side flanges 35, see Fig. 3, of a supporting bracket 36 secured by screws or the like 3S to the top housing wall 4, the franges 35 extending substantially parallel to the rear wall S. The upper end of the thrust member 2| is received in an aperture 31 in an operating lever 38 oi electric insulating material to which it is pivotally secured by a cross pin 39. The lever 38 is ulcrumed between the flanges 35 on bearing pins or screws 4! which are supported in the f r-ges S5. Also positioned between the flanges there is a switch arm 4| having parallel side members which extend between the sides of the ever 38 and the flanges 35, the arm being ulcrumed adjacent one end and end wall 3 on a bearing shaft 3 supported in the anges 35. rPhe free end of the lever 38 seats on an abutment member 44 such as a rod extending between the members 42. A helical coil spring 45 downward and seats on the switch arm 4| between its iulcrum and the end wall 3 and urges the abutment 44 upward against the lever 38. The spring seats at its upper end against the crc-ss member of the U-shaped bracket 36. The iree end or" the arm 4| which extends toward the end wall is provided with substantially parallel upper and lower armature portions 46, 41, the portion 4i' being secured to the arm 4| by spacer' sleeves and `:ets 4S or the like. The arm 4| is provided wit-n an upward projecting contact member 49 which extends through a slot in the armature portion 46 and is provided with a downward facing shoulder cooperable with the side edges of the slot to limit upward movement ol 'the armature portion. The contact member 4S is carried by a spring blade 50 which is riveted t0 the under race of the arm 4l, as at 5|. The contact member cooperates with a contact member which is secured in the top housing wall f and projects downward therefrom. lIhe contact member 52 is connected to a terminal post by a lead member 54 extending through and embedded in the top and the rear walls or the housing. The armature portion 46 cooperates with the poles of a U-shaped permanent magnet which extends longitudinally of the switch 4l in overlying relation to the armature portion e5, the poles of the magnet straddling the contact member' 52. The magnet 55 is secured by a nut and bolt 5B to a resilient hinge member such as a sheet metal angle plate rigidly secured to the end wall 2 by screws 58. An adjustment screwb having an operating knob 80 is adjustably screw-threaded in a metal insert 6| embedded in the top wall 4. The screw 59 proj s through 'the top Wall 4 and engages the head or colt S5 which is held in engagement with the screw by the inherent resilience of the hinge member 51, the screw being operable to swing the magnet poles against the resilience of the hinge member and toward the armature portion 4S to regulate the attractive force of the magnet acting on the switch arm 4|. Positioned beneath the magnet there is a base member 62 in the 'form or a hat supporting shelf which rests at one end on a shoulder 63 projecting from the end wall and which at its other end extends into a groove in a post or support 64 projecting from the rear wall E. The base member 52 is rigidly held in position by screws B5 extending through depending flanges on the front and rear edges of the member '62 and threaded into the rear wall 6. Supported on the member 62 there is a U-shaped permanent magnet 66 which is fulcrumed at its base end on the top face of the member 62. The magnet 6G extends longitudinally of the switch arm 4| with the free ends of its pole extending beneath the armature portion 41 lor cooperation therewith. The magnet '65 is supported in an upwardly inclined position with its poles spaced from the member 62 by a plate member 51 of resilient sheet metal which is bent or arched upwardly intermediate its ends and which has its opposite ends bearing on the top face of the member 62. A screw 68 extends through the magnet and is adjustably screwthreaded in the base member 62, the head of the screw 68 bearing on the top face of the magnet which is held in engagement with the screw head by the inherent resilience ol the plate 61. Adjustment oi 'thc screw G8 will regulate the position of the magnet poles relative to the armature portion 41. On the base member 62 between the magnet poles, there is a stop member 69 of electric insulating material which cooperates with a stop member 10 carried by the switch arm 4| to limit movement of the armature portion 41 toward the magnet C6 and to prevent engagement between the magnet and the armature portion 41. The stop member 10 projects through a slot in the arrca'l-ure portion 41 and is provided with a circumrerential shoulder engageable with the side edges of the slot, the stop member being carried by a spring blade 1| which is secured to but electrically insulated from the arm 4|, as at 12. The switch arm 4| is connected to a terminal post 13 by a lead wire 14 which is secured at one end, as at to the arm 4| and at its other end, as at l5, to a connector' strip 11 embedded in the housing wall and joined to the post 13.

Supported on the top wall 4 there is a casing 18 which is rigidly secured to the housing I by bolts T8. The casing 18 is preferably formed from a blank of sheet metal which is bent into substantially rectangular form with one end portion B turned upward into the casing to provide a lever support. Within the casing there is a lever member 8| which extends transversely to the side face of the support 8 and has lugs 82 which extend into apertures 83 in the support 80 to prevent displacement or the lever member and to serve as bearing points therefor. The lever member 3i is substantially U-shaped, having parallel arms 84, 85 which extend away from the support 8U. Positioned between the arm 84 and one end wall of the casing 18 there is a helical coil spring 8G which is under compression and which urges the lever member SI into engagement with a stop member 81' depending from the top wall of the casing i. The spring 86 is provided with end follower members 88 which are recessed, one receiving in its recess the pointed end of the arm 84, and the other receiving the pointed end of an abutment pin 89 adjustably screw-threaded in the end wall of the casing 13 to regulate the component o force of spring 38 acting on lever 8|. Through the tcp housing wall 4 there is an aperture 9D which receives an actuating member or push rod Si, the aperture overlying the free end portion of the switch arm 4| intermediate its fulcrum and armature portion 46 so that the rod 9| is movable downward into engagement with the switch arm to actuate the same. The rod 9| is provided with a head 92 providing a downward facing annular shoulder. Surrounding the rod 9| there is a helical coil spring 93 which bears at its upper end against the head 92 and at its lower end seats on an annular shoulder in the aperture 96 so that the spring 23 normally urges the rod 9i upward and holds the same out of en- Il i) 49 is held-closed by the attractive force of the magnet .55 for its armature portion 46 and the gag'ement with arm 4I and in engagement with the lever arm'85. The lever armf85 is provided with a conical downward facing recess which receives the conical upper end of the headed rod 9| `to insure their yoperative engagement with each other. On the top wall of the casing '18 there is a container 94 which is yof inverted cupshaped form, having a circumferential ange 95 which seats on the top casing wall and by` which the container' is rigidly secured tothe casing, preferably' by the screws 19. The container y94 is provided witha movable wall 96 which forms the head of a metal bellows 91 having its other end secured and sealed to an annular plate 98 c which is secured and sealed to the inside face of the side wall of container 94. The interior of the container 94 around the bellows 9,1 thus provides an expansible chamber 99 which is communicable with a source of fluid pressure through the bore of a fitting I secured and sealed in the top end wall of the container 94. A push rod or thrust member |0| is fixed at one end to the bellows head 96 and extends downward therefrom through the bellows and an aperture in the top wall of casing 'iii and terminates in a conical or tapered end portion which seats in a conical recess |62 in the top face of the lever member 8| adjacent its iulcrum and between the fulcrum support 80 and the push rod 9|, Surrounding the thrust member I9| there is an adjustable guide sleeve |93 which is adjustably screwthreaded in the ytop wall of the casing 18. Positioned between the sleeve member |03 and .the bellows head 56 thereis a helical coil spring `|04 f? which surrounds the thrust member |0I and which opposes expansion o1 the chamber 99. The force exerted by the spring |04 and the spring Q3 is preferably related to the component of force exerted by spring 86 so that the'increase of resistance of spring |04 and spring ,93 on movement of the bellows head 96 will be compensated by the decrease in resistance of the spring 86 to movement of the lever member 8| so that the force or pressure in chamber 99 which will initiate movement of lever member 8| will be suiiicient to carry the lever completely through its range of travel. It will be noted that the resistance of spring 93 will be opposed by the component of force of spring 86 as the lever member 3| moves overcenter but the force of spring 93 is at all times sufliciently greater than the component of force exerted by spring 86 so that when the force on the bellows head y96 decreases, the spring 93 can move the lever member upward to the position shown.

This control device is particularly adapted for use in connection with refrigerating apparatus and its operation will be described as employed in connection therewith although it will be apparent that the device is adapted for other uses. The fitting I is connected by suitable Vpiping to the refrigerant return line from the evaporator and the tting |00 is connected by suitable piping to the high pressure side of the system, for examce ple at the compressor outlet. The terminal posts 53 and I3 are connected by suitable lead wires to the compressor motor so that the control device will control the operation thereof. The control device is shown as having responded to Athe predetermined desired high pressure ,in the refrigerant return line which has closed the switch contacts to cause operation of the compressor. With the compressor in operation, the pressure in the refrigerant return line and therefore in chamber I 4 will decrease. The switch contact force of spring acting on the switch arm 4| together with the pressure in the chamber I4 which acts on the :bellows head I I.

i When the pressure has decreased to the predetermined degree at which operation of the compressor is to be stopped', the spring 2.2 will push downward `onthe thrust member 2| and turn the lever 38 -'clockwise about its fulcrum 40 which will pull Udownward on the abutment 44 and turn the switch arm 4| counterclockwise about its fulycrum 43 to separate contact member 49 from its contact member 52 to break the circuit between terminal posts 53 and 13. Contact between members 49 and 52 will be broken with a quick substantially snap action'due to the rapid decrease inthe holding force of magnet 55 for its armature vportion 46 as the lever arm 4| is moved The lost motion between blade 50 and arm 4I `also enhances the sharp breaking of contact as fthe arm 4| is in movement before the lost m0- tion is taken up. The downward movement of the armature portion 4l under the force of lever 38 will move the stop member 'I0 into engagement i' rwith its xed ystop rmember 460 and bring the armature portion 4-'I into the iield of its magnet 566, but the abutment member 44 will not leave the lever` 38 as -the spring 45 is suiiicient -to overcome the holding force of the magnet 66. 'it

With the compressor stopped, the pressure in chamber I4 will increase and when the pressure on the bellows head II plus the force of spring 45 becomes equal to the resisting force of spring 22 and the attractive force of magnet 66, then i the thrust member 2| will be moved upward.

The arm4| is held with its abutment 44 in engagement with the lever 38'by the spring 45 so that as the lever 38 is rotated counterclockwise about its fulcrum 40, the switch arm 4I will move with it to engage contact member 49 with its contact member 52 to start operation of the compressor. The snap or quick action of arm 4| above described also occurs when the arm 4I is moved to make contact due to the attractive force of magnet 66 for portion 4l. If it is desired to change the range of operation, that is, the mean pressure at which contact will be made and broken while maintaining a constant diierence between the pressure at which Contact is made and the pressure at which contact is broken, the force of the spring 22 is yadjusted by the operating member 32. If the operating member 32 is rotated to compress the spring 22 so that it exerts a greater force on the thrust member 2|, then the mean pressure in the chamber I 4 at which contact will be made and broken will be increased thereby resulting in a higher average evaporator temperature. Ii it is desired to decrease the temperature at which the compressor will be stopped without varying or changing the temperature at which the compressor is to be started, that is, to regulate the diierential at the switch cut-out point, then the magnet 55 is moved by its adjustment screw 59 toward the switch arm 4| which will increase the resistance to movement of the switch arm by the spring 22 so that the pressure in the chamber |4 must have a further vdecrease in pressure in order for the force of spring 22 to move the switch arm 4i as above described. This regulation of magnet 55 will not however affect the pressure in chamber I4 at which arm 4I will be moved upward to make contact. If it is desired to decrease the temperature at which the compressor is to be started, that is, to regulate the differential at the switch cut-in point, then the magnet 6G is moved by its screw toward the base member 62 against the force of resilient means 51 so that there will be a greater air gap between the armature portions 4": and the magnet poles when contact is broken and stop members 59 and 1!) are in engagement thereby requiring a lower pressure in chamber I4 and a less upward force on bellows head il to overcome spring 22 and the attractive force of magnet 66. Should the pressure on the outlet side of the compressor increase so that the force acting on the bellows head 96 will overcome the resisting force of springs 86, G3, and. then due to the compensation efiected by the reduction in the resisting component of spring 86, the plunger or thrust member will be moved quickly downward to carry the lever 8l and its spring 86 overcenter. As the lever Si moves downward, it will push downward on the actuating member or push rod SI and bring it sharply into engagement with the switch arm 4i to separate the contact member 49 from Contact member 52. The switch arm 4I is free to move downward under the force of push rod 9i due to the lost motion connection between the switch arm 4I and the lever 38 at abutment member fi, the attractive force of magnet 55 and the resistance of spring 45 only having to be overcome in order to break contact. Ii the pressure in the chamber 99 decreases due to stopping oi the compressor when Contact is broken by the safety mechanism, then when the pressure on the bellows head S6 has decreased sufficiently so that it will be overcome by the combined force of spring 93 and spring 104 less the resisting component of force of spring 85, the post Ei will be moved upward by the spring 93 which will hold lever member Si in engagement with plunger ii and permit the switch arm il to be moved to circuit making position under the force of spring 15. It will be noted that when contact is broken by downward movement of the push rod Si increased pressure in the chamber iai which will overcome spring 22 and move thrust member 2i upward will merely move the lever 38 awa-y from abutment 44 and will not act in opposition to the pressure in the chamber 99.

From the foregoing, it will be apparent that I nave provided a switch in which the range of operation may be adjusted by the control means 32 to regulate the pressures at which Contact vill be made and at which Contact will be broken without ariecting the differential of operation between these pressures. It will also be apparent that I have provided a switch in which the dif- "erential of operation may be increased or dec sed either by changing the pressure at which contact will be made or by changing the pressure t which contact will be broken or by changing both the pressure at which contact is made and the pressure at which contact is broken independently o the range oi operation of the device. Although the device is shown as adapted to respond directly to pressure, it is to be noted that the switch is equally operable by temperature responsive means requiring merely the connection of a volatile liquid containing bulb element to the fitting I5 or to the fitting |00 or to both of said ttings,

What I claim and desire to secure by Letters Patent of the United States is:

l. A device of the character described, comprising a. supporting structure, a control means,

an arm pivotally supported by said structure and operable to move said means, power means for moving said arm in one direction, a magnet cooperable vi h said arm and opposing operation of said arm by said power means, a spring for moving said arm in the opposite direction and opposing operation of said arm by said power means, a magnet cooperable with said arm and opposing operation of said arm by said spring, one of said magnets being mounted for pivotal movement whereby it is adjustable relative to said arm, and means to move the free end of said movable magnet.

2. A device of the character described, com prising a supporting structure, a control means, an arm pivotally supported by said structure and operable to move said means, power means for moving said arm in one direction, a magnet cooperable with said arm and opposing operation of said arm by said power means, a spring for moving said arm in the opposite direction and opposing operation of said arm by said power means, a magnet cooperable with said arm and opposing operation of said arm by said spring, resilient means supporting one of said magnets, and means to adjust said one magnet against the force of said resilient means and relative to said switch arm.

3. A device of the character described, comprising a supporting structure, a control means, an arm pivotally supported by said structure and operable to move said means, power means for moving said arm in one direction, a magnet cooperable with said arm and opposing operation of said arm by said power means, a. spring for moving said arm in the opposite direction and opposing operation of said arm by said power means, a magnet cooperable with said arm and opposing operation ol said arm by said spring, a resilient plate member supporting one of said magnets, and a screw engaging said one magnet and operable to adjust said one magnet against the force of said plate member'.

4, A device of the character described, comprising a supporting structure, a control means, an arm pivotally supported by said structure and operable to move said means, a lever separate from and engaging said arm, means holding said arm and said lever in engagement and operable to move said arm in one direction, a thrust member engaging said lever, means to move said thrust member to actuate said arm, and means directly engageable with said arm and operable to overcome said holding means, said last-named means acting through said arm to move said control means.

5. A device of the character described, comprising a supporting structure, a control means, an arm pivotally supported by said structure and operable to move said means, a lever separate from and engaging said arm, means holding said arm and said lever in engagement and operable to move said arm in one direction, a thrust member engaging said lever, means to move said thrust member to actuate said arm, an actuating member operable to overcome said holding means and to engage and move said arm relative to said lever, said actuating member acting through said arm to move said control means, overcenter means for moving said actuating member, and power means operable to move said last-named means overcenter.

6. A device of the character described, comprising a supporting structure, a control means, an

arm pivotally supported by said structure and operable to move said means, a lever separate from and engaging said arm, said lever being operable to move said arm, means holding said arm and said lever in engagement and operable to move said arm in one direction, a thrust member engaging said lever, means to move said thrust member` to actuate said arm, a magnet cooperable with said arm and opposing operation of said arm by said last-named means, and means operable to overcome said holding means and the attractive force of said magnet and to move said arm relative to said lever, said last-named means being directly engageable with and acting through said arm to move said control means.

7. A device of the character described, comprising a switch arm having a fulcrumy support, an expansible chamber having a movable wall, means for transmitting the movement of said Wall to said arm, a range spring cooperable with said wall and determining the pressure in said chamber at which contact will be made and broken, a magnet cooperable with said arm and determining the pressure in said chamber at which contact will be made, a second magnet cooperable with said arm and determining the pressure in said chamber at which contact will be broken, one of said magnets being mounted for pivotal movement whereby it is adjustable relative to said arm, and means to move the free end of said movable magnet.

8. A device of the character described, comprising a switch arm having a fulcrum support, an expansible chamber having a movable wall, a lever separate from and engageable with said arm and operable to transmit the movement of said wall to said arm, means acting on said arm to hold said arm in engagement with said lever, means to move said arm relative to said lever, a range spring cooperable with said wall and determining the pressure in said chamber at which contact will be made and broken, a magnet c0- operable with said arm and determining the pressure in said chamber at which contact will be made, said holding means exerting a greater turning moment on said arm than does said magnet whereby said holding means acts alone to overcome the attractive force of said magnet, and a second magnet cooperable with said arm and determining the pressure in said chamber at which Contact will be broken.

9. A device of the character described, comprising a switch arm having a fulcrum support, an expansible chamber having a movable wall, means for transmitting the movement of said wall to said arm, a range spring cooperable with said wall and determining the pressure in said chamber at which contact will be made and broken, a magnet cooperable with said arm and determining the pressure in said chamber at which contact will be made, said magnet being mounted for pivotal movement and extending longitudinally of and overlying said arm, and a second magnet cooperable with said arm and determining the pressure in said chamber at which contact will be broken, said second-named magnet being mounted for pivotal movement and extending longitudinally of and underlying said arm and said first-named magnet.

10. A device of the character described, comprising a supporting structure including a base member, a switch arm fulcrumed on said structure, a magnet having one end fulcrumed on said base member and having its other end extending into cooperable spaced relation to said arm, resilient means positioned between said base member and said other magnet end and urging said magnet toward said arm, and adjustablemeans securing said magnet to said base member, said adjustable means being operable to regulate the position of said other magnet end relative to said arm.

11. A device of the character described, comprising a supporting structure including a base member, a switch arm fulcrum'ed on said structure, a magnet having one end fulcrumed on said member and having its other end extending into cooperable spaced relation to said arm, resilient means positioned between said base member and said other magnet end and urging said magnet toward said arm, adjustable means securing said magnet to said base member, said adjustable means being operable to regulate the position of said other magnet end relative to said arm, and means on said base member to limit movement of said arm toward said magnet.

l2. A device of the character described, comprising a housing, a switch arm fulcrumed in said housing, power means to actuate said arm, a push rod extending through the Wall of said housing and engageable with said arm, a casing secured on said housing and receiving said rod, a lever fulcrumed in said casing and bearing on said rod, a spring in said casing and engaging said lever, said spring acting on said lever at an acute angle and being movable overcenter to exert its force through said lever to move said push rod to actuate said arm, and means to move said lever to move said spring overcenter.

13. A device of the character described, comprising a housing, a switch arm fulcrumed in said housing, power means to actuate said arm, lostmotion means operatively connecting said power means and said arm, a push rod extending through the wall of said housing and engageable with said arm, means normally acting tomaintain said push rod out of contact with said arm whereby movement of said arm is unimpeded by said rod, a casing secured on said housing and receiving said rod, a lever fulcrumed in said casing and bearing on said rod, a spring in said casing and engaging said lever, said spring acting on said lever at an acute angle and being movable overcenter to exert its force through said lever to move said push rod to actuate said arm, and means to move said lever to move said spring overcenter. l

14. A control device comprising a supporting structure, a movable member pivotally supported by said structure and movable for controlling an electric circuit, power means operable for moving said member in one direction, resilient means for moving said member in the opposite direction and opposing operation of said member by said power means, means cooperable with said member and yieldably opposing operation of said member by said resilient means, a magnet cooperable with said member and opposing operation oi said member by said power means, said magnet being mounted for pivotal movement whereby it is adjustable relative to said member, and means operable to move the free end of said movable magnet.

l5. In a control device having a movable switch member for controlling the circuit and operation of an electrically operated refrigerating apparatus and normally actuated by a power means responsive to changes in a fluid characteristic at one point in said system, a snap acting device for moving said switch to open said circuit upon a predetermined change in the characteristic of said iiuid at another point in said system comprising, a. push rod normally positioned out of engagement with said switch member and movable to engage therewith to move said switch member to open position, yieldable means exerting a force and normally acting to hold said push rod in its normal position, a pivotal lever member in engagement with said push rod, a spring having one end iixed and its other end in engagement with the free end of said lever member with the point or" engagement therebetween normally positioned overcenter in one direction, and a power means responsive to said predetermined change in the fluid characteristic at said secondnamed point in said system and having a thrust member for moving said lever to move its point of engagement with said spring overcenter in the opposite direction to move said push rod with a snap action into engagement with and move said switch member to open position, said resilient means exerting a greater force than the force exerted by said spring means and operable to return said spring means and said lever to their normal overcenter position upon a predetermined decrease in the force of said second-named power means.

i6, In a control device ior controlling iiow in a uid flow system and having a control means actuated through a pivotal lever by a power means responsive to changes in a characteristic of the fluid in one point of the system, a device for actuating said control means upon a predetermined change in the characteristic of the iiuid in another point of said system comprising, a push rod normally positioned in spaced relation to said lever member and movable to engage and move said lever member to actuate said control means, a spring for holding said push rod in its normal position, a pivotal lever member engaging said push rod, a coil spring having one end engaging the free end of said second-named lever member with the point of engagement therewith normally being positioned overcenter in one direction, land a power means responsive to said predetermined change in the characteristic of the fluid at said second-named point in said system, said power means having a thrust member engaging said second-named lever member to move its point of engagement with said second-named spring overcenter in the opposite direction to move said push rod to engage and move said first-named lever member with a snap action, said first-named spring exerting a greater force than the component force exerted by said secondnamed spring acting thereagainst and operable to automatically return said second-named spring and said second-named lever member to their normal overcenter position upon a predetermined decrease in the force exerted by said secondnamed power means.

17. A device of the character described, comprising a pair of parallel longitudinally reciprocal thrust members, a control means, an arm operable to actuate said control means and extending transversely to said thrust members, one of said thrust members acting directly on and through said arm to actuate said control means. a lever pivotally supported and independent oi said arm, said lever acting on and through said arm to actuate said control means, the other of said thrust members being operatively connected to and for moving said lever, and means urging said lever and said arm into cooperable engagement and opposing operation of said arm by said thrust members.

18. In a control device, a. power element having a movable wall, a plunger operable by said wall, a control means, a thrust member longitudinally reciprocal and operable to actuate said control means, a lever for transmitting movement from said plunger to said thrust member, and a spring having one end engaging said thrust member, said spring acting to hold said thrustmember out of engagement with said control means and in engagement with said lever and to hold said lever in engagement with said plunger,

EARNEST J. DILLMAN. 

